Conventionally, a metallic substrate formed of, for example, an aluminum alloy is widely employed as a substrate for producing a magnetic recording medium. Usually, such a metallic substrate undergoes texturing, and is employed for producing a magnetic recording medium.
Texturing is a process for forming an irregular surface on a substrate along a predetermined direction (usually in a circumferential direction) of the substrate. When the surface of a substrate undergoes texturing, the crystalline orientation of an undercoat film and a magnetic film, which are formed on the substrate, is enhanced, and the magnetic film exhibits magnetic anisotropy. Thus magnetic characteristics, such as thermal stability and resolution, of a magnetic recording medium can be enhanced.
In recent years, instead of a metallic substrate formed of aluminum or similar metal, a non-metallic substrate formed of material such as glass or ceramic has been widely employed as a substrate for producing a magnetic recording medium. Such a non-metallic substrate has an advantage that head slap does not easily occur in the substrate, because of the high hardness of the substrate.
However, in the case in which a non-metallic substrate such as a glass substrate is employed, the magnetic film may not be imparted with satisfactory magnetic anisotropy even when the substrate undergoes texturing. As a result, the resultant magnetic recording medium may exhibit unsatisfactory magnetic characteristics.
In order to solve such problems, formation of a hard film which can be easily textured on a non-metallic substrate formed of material such as glass or ceramic has been proposed.
For example, Japanese Patent Application Laid-Open (kokai) No. 5-197941 discloses a magnetic recording medium including a non-metallic substrate formed of material such as glass or ceramic, and the substrate is coated through sputtering with NiP film serving as a hard film which is easily textured.
Japanese Patent Application Laid-Open (kokai) Nos. 4-29561 and 9-167337 disclose a magnetic recording medium including a non-metallic substrate which is plated with film such as electroless plating film, and the film serves as a hard film.
A magnetic recording medium including a hard film formed on a non-metallic substrate is produced through the following process: the hard film is formed on the substrate in a film formation apparatus such as a sputtering apparatus; the substrate is temporarily removed from the apparatus and is subjected to texturing by use of a texturing apparatus; the resultant substrate is again placed in the apparatus; and then an undercoat film and a magnetic film are formed on the substrate.
However, the aforementioned conventional production process for a magnetic recording medium includes complicated production steps, resulting in high production costs. Therefore, there has been keen demand for a production process for a magnetic recording medium, which encompasses a simplified production procedure.